GILBERT, M.R.; BELTR�N, J.L.; PORTER, M.E.; SUMMERS, A.P.; Univ. of California, Irvine; Univ. of California, Irvine; Univ. of California, Irvine; Univ. of California, Irvine: Biochemistry and material properties of cartilage from four species of shark.

In most vertebrates, cartilage plays just two functional roles � a low friction bearing surface (as in your knees) and contour filler (your nose and ears). However, a successful group of vertebrates, the class Chondrichthyes (sharks, ratfish and rays), has an entirely cartilaginous skeleton implying a far broader range of function for this connective tissue. We investigated the biochemical composition of cartilage from four species of shark (silky, pelagic thresher, smooth hammerhead and shortfin mako) and performed preliminary material property tests on these same species. Mammalian cartilage is primarily composed of water, proteoglycan (PG) and collagen. Shark cartilage like mammalian cartilage is about 25% dry matter. In our samples, collagen was far less abundant than in mammalian cartilage (15-35% DW vs 50%), while PG (3-6% DW) was similar though more variable. About half the dry weight of cartilage remains unknown. Eight and 10mm cylinders, 4-6mm long were cut from jaws with a trephine. Force-extension was measured via static compressive tests to failure. There were two-fold variations in the stiffness of cartilage and significant variation in strength among species.